A Disk-Shaped Antenna with Reconfigurable Axial Ratio Beam

A novel technique is proposed to achieve a circularly polarized antenna. The circle patch placed in the center is excited by four ports with equal amplitude and 90° phase difference, and the double-ring parasitic patch with varactor is placed around the circle patch. The ARBW (axial ratio beam width) of the antenna is changed symmetrical or asymmetrical, the maximum radiation direction as the symmetry point, through adjusting the capacitance value of the varactor. The inner-ring of the double-ring parasitic obtains current through the coupling with the circle patch which is a radiation structure, then the current on the inner-ring flows to the outer-ring, and then the far field of circularly polarized antenna is adjusted by controlling the electrical length of the outer-ring, finally, the change of the far field of the circularly polarized antenna will cause the variation of ARB.